In general, with a mobile communication system, a cell size determination or a cell arrangement is properly performed taking into consideration of the expected number of mobile stations located in the coverage of each cell or the expected communication data quantity. In this manner, the operator structures the system in order to provide the communication service of certain quality and, therefore, the users of the mobile terminals can receive the communication service without being bothered by any limitation placed on time and place.
However, in some cases, e.g., when many people gather at a specific location of any event, or when a natural disaster occurs, an enormous amount of access requests may be made to a specific base station or a specific switching center, whereby congestion may occur.
As a method for preventing a reduction in the performance of the system function upon the occurrence of congestion, Patent Literature 1 discloses a congestion control method. According to this method, mobile terminals located in the service area of a base station are managed as a group. When congestion occurs, restriction information data is transmitted to the mobile terminals belonging to a group being the target of a restriction. Then, each mobile terminal receiving the restriction information data extracts the restriction start time and the restriction removal time of the group to which the mobile terminal itself belongs, and displays the data on a display unit such as liquid. Accordingly, each user can tell that the talk and communication functions of his/her mobile terminal are in the operation-stopped state, and when the functions become available. Further, execution of a communication restriction can prevent the congestion state from being continued.
Further, Patent Literature 2 discloses a method for restricting access requests from mobile stations when lines cannot be secured due to an enormous amount of access requests triggered by disaster situations or the like. According to the access restriction method, each base station transmits transmission restriction information via a broadcast channel. When mobile stations receive the transmission restriction information sent via the broadcast channel, they each determine whether or not the access restriction is imposed on the self station. When the access restriction is imposed on the self station, transmission of the self station is prohibited, except for the case where a call is received or in the case of emergency communication. What is further included is an output function for broadcasting the users about the restriction and the removal thereof. Accordingly, even in disaster situations, it becomes possible to prevent access requests from temporarily occupying the wireless lines.